Largest prime < 10*a(n-1), a(1)=7.

Terms

a(0) =7a(1) =67a(2) =661a(3) =6607a(4) =66067a(5) =660661a(6) =6606581a(7) =66065773a(8) =660657713a(9) =6606577129a(10) =66065771269a(11) =660657712667